1. Field of the Invention
This invention relates to data display systems and more particularly to a display terminal which provides the architecture and electrical interface for the attachment of feature devices to expand the capability of the terminal in a modular fashion.
2. Description of the Prior Art
Display systems are known which include optional accessories such as a card reader, and light pen. These features are interfaced to the display by individually specialized logic, and whenever an additional feature is required, an additional interface is required. Some systems include special features, such as graphics and special effects capabilities which are built into the display unit. Other prior art systems make use of a system bus, with a microprocessor, a display unit with a keyboard, and other units such as auxiliary storage, etc., connected to the bus.
Prior art systems of the kind described have built-in, relatively tailor made characteristics whereby the tendency is to design and build various separate models for different employments.